1. Field of the Invention
The invention relates to a double patterning method.
2. Discussion of the Background
A reduction in dimensions of a resist pattern used for a lithographic process has been desired along with miniaturization of various electronic device structures (e.g., semiconductor devices and liquid crystal devices). A fine resist pattern having a line width of about 90 nm can be formed using a chemically-amplified photoresist composition, and using ArF excimer laser light or the like as exposure light. However, a finer resist pattern will be required in the future.
In recent years, a double patterning technique that forms a resist pattern two or more times has been proposed as a technique that improves the resolution of a resist pattern (see SPIE 2006 61531K). The double patterning technique repeats a patterning process that forms a resist film using a positive-tone resist composition, and subjects the resist film to exposure and alkali development. It is considered that a resist pattern having a resolution higher than that of a resist pattern formed by a single patterning process can be formed by the double patterning technique.
However, the double patterning technique has a problem in that deformation, dissolution, or the like of the first resist pattern may occur when forming the second resist pattern due to the solvent included in the photoresist composition, the effects of exposure, or the like, and a large difference in pattern height may occur, or the pattern may not have a rectangular cross-sectional shape. The double patterning technique has another problem in that it is difficult to form a pattern having both a narrow area and a wide area.
In order to solve the above problems, a technique that insolubilizes the surface of the first resist pattern (see Japanese Patent Application Publication (KOKAI) No. 2009-69817), and a technique that forms the second resist pattern using a negative-tone resist composition that includes an alcohol-based organic solvent (see Japanese Patent Application Publication (KOKAI) No. 2008-78220) have been proposed.